Crystal structure and Hirshfeld surface analysis of 2-amino-6-[(1-phenylethyl)amino]-4-(thiophen-2-yl)pyridine-3,5-dicarbonitrile

In the crystal, the molecules are connected by N—H⋯N hydrogen bonds into dimers with an (12) motif, forming chains along the b-axis direction. These chains are linked to each other by N—H⋯N hydrogen bonds, N–H⋯π and π–π interactions, forming a three-dimensional network.

In the title compound, C 19 H 15 N 5 S, the thiophene ring is disordered in a 0.6:0.4 ratio by an approximate 180 rotation of the ring around the C-C bond linking it to the pyridine ring. In the crystal, the molecules are linked by N-HÁ Á ÁN hydrogen bonds into dimers with an R 2 2 (12) motif, forming chains along the b-axis direction. These chains are connected to each other by further N-HÁ Á ÁN hydrogen bonds, forming a three-dimensional network. Furthermore, N-HÁ Á Á and -[centroid-centroid separations = 3.899 (8) and 3.7938 (12) Å ] interactions also contribute to the crystal cohesion. A Hirshfeld surface analysis indicated that the most important contributions to the surface contacts are from HÁ Á ÁH (46.1%), NÁ Á ÁH/HÁ Á ÁN (20.4%) and CÁ Á ÁH/HÁ Á ÁC (17.4%) interactions.

Chemical context
Diverse C-C, C-N and C-O bond-formation methods play important roles in organic synthesis. The reaction scopes have also been greatly expanded, employing these methods in different fields of chemistry, in both academia and industry (Ç elik et al., 2023;Chalkha et al., 2023;Tapera et al., 2022;Gurbanov et al., 2020;Zubkov et al., 2018). The pyridine moiety is a widespread structural motif that can be found in various natural products and pharmacologically active compounds. 3,5-Dicyanopyridines have been reported as intermediates in the synthesis of pyrido[2,3-d]pyrimidines, pyridothienotriazines, azabenzanthracenes and pyrimidine Snucleoside derivatives with a broad spectrum of biological activity (Cocco et al., 2005;Zhang et al., 2022;Poustforoosh et al., 2022). The design of new 3,5-dicyanopyridine derivatives is thus of great interest.

Figure 2
View of the molecular packing along the a axis. N-HÁ Á ÁN hydrogen bonds are shown as dashed lines. For clarity, the minor disorder component is not shown.

Figure 1
The molecular structure of the title compound, showing the atom labelling and displacement ellipsoids drawn at the 30% probability level. For clarity, the minor disorder component is not shown. Table 1 Hydrogen-bond geometry (Å , ).

Table 2
Summary of short interatomic contacts (Å ) in the title compound.

Contact
Distance Symmetry operation View of the molecular packing along the b axis. Hydrogen bonds are shown as dashed lines.

Database survey
The four related compounds found as a result of the search for '2,6-diamino-4-(thiophen-2-yl)pyridine-3,5-dicarbonitrile' in the Cambridge Structure Database (CSD, Version 5.42, update of September 2021; Groom et al., 2016)  In the crystal of MUCLAA (space group P2 1 /c), chains running along the b-axis direction are formed through N-HÁ Á ÁO interactions between the 1,4-dihydropyridine N atom and one of the O atoms of the ester groups. Neighbouring chains are linked by C-HÁ Á ÁO and C-HÁ Á Á interactions. In the crystal of WOJCIJ (space group P2 1 /c), inversion dimers linked by pairs of N-HÁ Á ÁN hydrogen bonds generate R 2 2 (16) loops and the dimers are linked by C-HÁ Á Á and aromaticstacking interactions into a three-dimensional network. In WOPLAQ (space group P2 1 /n), inversion dimers linked by pairs of N-HÁ Á ÁN c (c = cyanide) hydrogen bonds generate R 2 2 (16) loops. In DOPWOW (space group Pbca), inversion dimers linked by pairs of N-HÁ Á ÁN n (n = nitrile) hydrogen bonds generate R 2 2 (16) loops. Aromaticstacking and very weak C-HÁ Á Á interactions are also observed.

Synthesis and crystallization
To a solution of 2-(thiophen-2-ylmethylene)malononitrile (0.82 g; 5.1 mmol) and malononitrile (0.34 g; 5.2 mmol) in methanol (25 mL), phenylethylamine (0.63 g; 5.2 mmol) was added and the mixture was stirred at room temperature for 48 h. Then 15 mL of methanol were removed from the reaction mixture, which was left overnight. The precipitated crystals were separated by filtration and recrystallized from ethanol/water (1:1) solution (yield 94%; m.p. 460-461 K).   related by an approximate rotation of 180 about the C4-C15 bond in a 0.6:0.4 ratio. EADP commands in SHELXL were used for the U ij values of equivalent atom pairs (e.g., C16 and C16A) and DFIX commands were used to restrain the nearest-neighbour and next-nearest-neighbour bond distances in the two disorder components to be equal with a standard deviation of 0.03 Å . All C-bound H atoms were placed in calculated positions (0.95-1.00 Å ) and refined as riding with U iso (H) = 1.2 or 1.5U eq (C). The N-bound H atoms were located in a difference map and refined with U iso (H) = 1.2U eq (N) [N2-H2 = 0.91 (3) (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2020).  (Rigaku OD, 2022); Numerical absorption correction based on Gaussian integration over a multifaceted crystal model; Empirical absorption correction using spherical harmonics implemented in SCALE3 ABSPACK scaling algorithm. Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refined as a 2-component inversion twin.